1. Field of the Invention
The present invention relates to a medical device designed for implantation within a vessel of the body, and more particularly, to a stretch resistant vasoocclusive coil for the treatment of aneurysms. The vasoocclusive coil is particularly suited for use in cases where it may be necessary to reposition the coil once the coil has been initially placed within the vessel.
2. Description of the Prior Art
For many years, vasoocclusive devices have been used to occlude blood vessels at specific treatment locations. These devices take many different forms including helically wound coils, coils wound within coils, or other such coil configurations. Examples of various coil configurations are disclosed in U.S. Pat. No. 5,334,210, entitled “Vascular Occlusion Assembly;” and U.S. Pat. No. 5,382,259, entitled, “Vasoocclusion Coil with Attached Tubular Woven or Braided Fibrous Covering.” Embolic coils are generally formed of a radiopaque metallic material, such as platinum, gold, tungsten, or an alloy of these metals. Often, several coils are placed at a given location to occlude, or partially occlude, the flow of blood through the vessel or aneurysm by promoting thrombus formation at the particular location.
Flexible catheters have been used to place various devices or medications within the vasculature of the human body. Such devices or medications include dilation balloons, radiopaque fluids, liquid medications, and various types of occlusion devices such as balloons and embolic coils. Examples of such catheter-based devices are disclosed in U.S. Pat. No. 5,108,407, entitled “Method and Apparatus for Placement of an Embolic Coil;” and U.S. Pat. No. 5,122,136, entitled “Endovascular Electrolytically Detachable Guidewire Tip for the Electroformation of Thrombus in Arteries, Veins, Aneurysms, Vascular Malformations and Arteriovenous Fistulas.” These patents disclose catheter-based devices designed to deliver embolic coils to a predetermined site within a vessel of the human body in order to treat aneurysms, or alternatively, to occlude a blood vessel at a particular location.
Additionally, embolic coils have been placed within the distal end of a catheter, such that when the distal end of the catheter is properly positioned, the coil may then be pushed out of the end of the catheter with a pusher member to release the coil at the predetermined site within the vessel. This procedure for placement of the embolic coil is conducted under fluoroscopic visualization, such that the movement of a coil through the vasculature of the body may be monitored, and the coil may be placed in the desired location.
To prevent stretching of the embolic device, especially during post-deployment retrieval, or repositioning during delivery, embolic devices often take the form of an embolic coil having a lumen extending therethrough and a stretch resistant member extending through the lumen. In one embodiment, the stretch resistant member takes the form of a fiber which is attached to the proximal and distal ends of the coil. In another embodiment, the stretch resistant member is fixedly attached to the distal end of the embolic coil, is extended through the lumen of the coil, and is detachably connected to a proximal end of an elongated pusher member. The connection between the pusher member and the coil may be severed by application of heat to the stretch resistant member, typically formed of a thermoplastic material. Such a device is disclosed in U.S. Patent Publication No. 2004/0034363, entitled “Stretch Resistant Therapeutic Device.”
Another variation of a stretch resistant embolic device includes a helically wound outer coil with a stretch resistant member extending therethrough. In order to prevent stretching during movement of the coil, the stretch resistant member is fixedly attached to the coil in at least two locations, such as the proximal end and the distal end. The coil may take on a secondary shape when it is released from the delivery device. Such a device is disclosed in U.S. Pat. No. 5,853,418, entitled “Stretch Resistant Vaso-occlusive Coils (II).”
Yet another embodiment of a stretch resistant coil includes a stretch resistant member, such as a fiber, which extends through at least a portion of a primary coil having proximal and distal ends. The stretch resistant member is attached to the primary coil at two axially separated locations to prevent or minimize axial stretching of the coil. One of these attachment locations is created with an anchor assembly disposed within the lumen of the coil. The anchor assembly takes the form of a coil that is incorporated into the windings of the primary coil. Such a device is disclosed in U.S. Patent Publication No. U.S. 2004/0002733, entitled “Integrated Anchor Coil in Stretch-Resistant Vaso-occlusive Coils.”
Still another embodiment of a stretch resistant coil and delivery system takes the form of an interlocking coupling between a pusher member and a thin wire affixed to an embolic coil. The thin wire may be affixed to a distal, intermediate or proximal location on the coil and includes a ball shaped member fixedly attached to the proximal end of the wire. In order to position the coil at the treatment site, a pusher member with a ball member affixed to its distal end releasably interlocks with the ball member at the proximal end of the stretch resistant member. Such a device is disclosed in U.S. Pat. No. 5,304,195, entitled, “Detachable Pusher-Vasoocclusive Coil Assembly with Interlocking Coupling.”
Another embodiment of a stretch resistant embolic coil includes an embolic coil with a stretch resisting member extending through its lumen and being attached to the coil in at least two locations. The stretch resistant member is somewhat loose within the lumen of the embolic coil, and the coil may take on a secondary shape after release within the body. Such a device is disclosed in U.S. Pat. No. 5,853,418, entitled, “Stretch Resistant Vaso-occlusive Coils (II).”
Even another embodiment of a stretch resistant embolic coil includes a coil with proximal and distal ends reinforced with a stretch resistant member extending therethrough. The distal end of the stretch resistant member is fixedly attached at the distal end of the coil, and the proximal end of the stretch resistant member is detachably mounted on an elongated pusher member at its distal end. Such a device is disclosed in U.S. Patent Publication No. 2005/0043755, entitled, “Vasoocclusive Coil with Enhanced Therapeutic Strand Structure.”
Yet another embodiment of a stretch resistant embolic coil includes a wire that is wrapped with a polymer and is helically wound. A stretch resistant member may extend though the lumen of the coil and is attached to at least two points on the coil. Such a device is disclosed in U.S. Pat. No. 6,280,457, entitled, “Polymer Covered Vaso-occlusive Devices and Methods of Producing Such Devices.”
Still another embodiment of a stretch resistant embolic coil includes an outer coil and at least one inner co-axial member. When the outer coil is subjected to axial tension it lengthens axially and contracts radially. The radial contraction is resisted by the inner co-axial member. Such a device is disclosed in U.S. Patent Publication No. 2004/0006363, entitled, “Coaxial Stretch Resistant Vaso-Occlusive Device.”